As described in, for example, Patent Literature 1, silicone resins are excellent in characteristics, such as transparency, heat resistance, light resistance, etc., and also excellent in hardness and rubber elasticity, and therefore, the silicone resins are used in a sealing material for optical semiconductor, an optical waveguide material, and the like.
In particular, as a sealing material of a light emitting diode (LED) that is one of optical semiconductor light emitting elements, there are organic modified silicone resins and phenyl (or methyl phenyl) silicone resins as described in, for example, Patent Literature 2; dimethyl silicone resins as described in, for example, Patent Literature 3; and the like.
Meanwhile, while the silicone resins are excellent in durability, there is involved such a problem that gas permeability is large (gas barrier properties are low), and in response thereto, it has been attempted to incorporate a metal oxide particle. In order to make a transparent composite by using the silicone resin and the metal oxide particle, the particle surface must be treated with an organic silane agent. For example, as described in Patent Literatures 4 and 5, by applying a surface treatment with an epoxy group-containing silane agent or a vinyl group-containing silane agent, it becomes possible to prevent aggregation of the particles at the time of curing of the resin, thereby producing a transparent composite.